Conventional illumination systems or light sources have been used for many years in general lighting and in lighting for decoration, advertising, warning, guidance and entertainment applications. Such light sources utilize a variety of lights, including but not limited to incandescent, Halogen and Fluorescent types, which are subject to many drawbacks. For example, halogen and incandescent lights produce undesirable heat and are limited to producing only white or yellow light. Additionally, these conventional light sources may also have limited longevity with lifetimes significantly less than a few thousand hours. Such light sources are also susceptible to breakage in high shock and vibration prone environments.
Light Emitting Diode (LED) sources have recently undergone significant advances, which enables them to be a cost effective replacement for conventional light sources. LED light sources offer significant benefits over conventional light sources as they consume less electrical energy for a given light intensity while exhibiting much longer lifetimes. Other desirable properties of LEDs include high resistance to shock or vibration, low heat dissipation, very fast switching response times and a wide choice of illuminating colors.
LEDs are illuminated solely by the movement of electrons in a semiconductor material. The LED consists of a chip of semiconducting material impregnated, or doped, with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon, i.e. light.
Most materials used for LED production have very high refractive indices which causes much of the light emitted from the diode to be reflected back in to the material at the material's surface containing the diodes. The light that is reflected back is then absorbed and turned into additional heat. As of result, this inefficiency causes an increase of heat and lower light output as the light is being reflected onto the material/diode. As a consequence of the increased heat, with existing LED technology, each LED must be treated individually or one chip at a time. For example, a LED flashlight utilizes clusters of LEDs and each LED in the cluster of LEDs is treated individually. If the LEDs are not treated individually, the LED chip produces undesirable heat as a result of the refractive indices as described above.
Accordingly, a need exists for illumination methods and systems that overcome the drawbacks of conventional illumination systems and that take advantage of the possibilities offered by overcoming such drawbacks.